Control of a charged, piston internal combustion engine having a plurality of exhaust gas turbochargers

ABSTRACT

One of the exhaust gas turbochargers of a plurality of parallel turbochargers is constructed to be disconnectable and connectable by the arrangement of one controllable exhaust gas blocking device in the exhaust gas pipe in front of the exhaust gas turbine and one automatically operating charge air blocking device in the suction pipe of the charge air compressor. A fast power increase to the nominal power of the internal-combustion engine is achieved, if a bypass pipe with a controllable bypass blocking device is arranged at the switchable exhaust gas turbocharger, this bypass blocking device being constructed as a transverse connection between the suction pipe of the charge air compressor of the exhaust gas turbocharger, which cannot be disconnected, and the suction pipe of the charge air compressor downstream of the charge air blocking device of the disconnectable and connectable exhaust gas turbocharger. The thermal and mechanical overloading of the connected exhaust gas turbocharger is therefore avoided.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a charged piston internal combustionengine having several parallel-operating exhaust gas turbochargers.

In piston internal combustion engines, exhaust gas turbochargers, forincreasing the charge air pressure and the charge air volume, are shutdown when the yield of exhaust gas energy is reduced in comparison tothe full-load operation. This condition occurs, for example, in thepartial-load and partial-speed operation of the piston internalcombustion engine. In this case, when there is a low yield of exhaustgas energy, only one exhaust gas turbocharger is operated; however, whenthe power of the piston internal combustion engine increases, graduallyone or several further exhaust gas turbochargers are connected inparallel until finally, during the full-load operation of the engine,all existing exhaust gas turbochargers will be operating.

A piston internal combustion engine of this type is disclosed by GermanPatent Applicaiton (DE) 34 11 408 C2. When the load of the pistoninternal combustion engine is low, one exhaust gas turbocharger isdisconnected from the exhaust gas collector pipe by an exhaust gasblocking device controlled by the charge air pressure. In this case, acharge air blocking device in the suction pipe of the charge aircompressor prevents charge air from flowing out of the charge aircollector pipe and into the suction pipe. The momentarily existingcharge air pressure builds up all over the compressor part of thedisconnected exhaust gas turbocharger from the direction of the chargeair collector pipe and leading to the charge air blocking device.

This arrangement has a disadvantage in that the requirement of a rapidand high power increase can be met only insufficiently because thepiston internal combustion engine cannot follow rapid variations of adesired load requirement before the connecting operation of a previouslydisconnected exhaust gas turbochargers is concluded. This connectionsequence of disconnected turbochargers is delayed by the fact that thecharge air compressor of the disconnected exhaust gas turbocharger needssome time in order to reduce the charge air pressure, which at firststill exists in its suction pipe downstream of the charge air blockingdevice, to the opening pressure of the charge air blocking device.

It is another disadvantage of the above-noted arrangement in that therunning parts of the connected exhaust gas turbocharger are firstaccelerated to an overspeed which is also a result of the delayedpressure reduction in the suction pipe of the pertaining charge aircompressor. The reason is that, as long as no pressure difference existsat the charge air compressor between the suction and the pressure sidethereof, its power intake is low in comparison to the driving poweralready available at the assigned exhaust gas turbine. The equilibriumbetween supplied and taken in power of an exhaust gas turbocharger, atthe point in time of the start of the connecting operation, takes placein an area of the characteristic diagram of the exhaust gas turbochargerwhich has an unacceptably high rotational speed. However, this highrotational speed results in thermal as well as mechanical stress to therunning parts of the exhaust gas turbocharger reducing its durability.

The described disadvantages occur in piston internal combustion engineswith single-stage as well as with dual-stage charging. The onlydifference is that, in the case of a single-stage charging, bothproblems occur at the same exhaust gas turbocharger and, in the case ofa dual-stage charging, the switching delay relates to the low-pressureexhaust gas turbocharger and the overspeed problem relates to thehigh-pressure exhaust gas turbocharger.

It is therefore an object of the present invention to provide anarrangement for a piston internal combustion engine of theabove-mentioned type which permits a fast power connecting operation tothe nominal output and avoids thermal and/or mechanical overloading ofthe exhaust gas turbocharger to be connected.

According to the invention, this object and other objects are isachieved by the opening of a bypass blocking device at the point in timeof the triggering of the connecting operation which causes an immediatepressure relief in the suction pipe of the connected charge aircompressor. The conditions that are required for an optimal operation ofthe connected exhaust gas turbocharger are therefore obtained veryrapidly on the air side at the connected exhaust gas turbocharger.

For a piston internal combustion engine of the above-mentioned type witha dual-stage charging, an advantageous further embodiment of theinvention is also provided.

Principal advantages achieved by preferred embodiments of the inventioninclude that interference with the power increase by the switching delayis eliminated when an exhaust gas turbocharger is connected; that theoverspeed occurring during the connecting of an exhaust gas turbochargeris avoided; that in dual-stage charging, the acceleration of theconnected low-pressure exhaust gas turbocharger is also improved; andthat a simple control of the blocking device is obtained which controlsthe bypass pipe arranged between the suction pipes of the charge aircompressor since a monitoring with respect to the closing is absent.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a supercharging aggregate with two single-stageexhaust gas turbochargers of a piston internal combustion engine;

FIG. 2 is a view of a bypass blocking device with an automaticallylocking part according to Detail II in FIG. 1 and FIG. 3;

FIG. 3 is a view of a supercharging aggregate with two dual-stageexhaust gas turbochargers of a piston internal combustion engine;

FIG. 4 is a bypass blocking device with a controlled locking partaccording to Detail IV in FIG. 3;

FIG. 5 is a view of an exhaust gas blocking device with the exhaust gasbypass pipe according to Detail V in FIG. 3;

FIG. 6 is a cross-sectional view of a connecting piece of an exhaust gasturbine in the area of the exhaust gas bypass mouth according to LineII--II in FIG. 7;

FIG. 7 is a longitudinal sectional view of an exhaust gas turbine and aconnecting piece according to Line III--III in FIG. 6;

FIG. 8 is a supercharging aggregate with two dual-stage exhaust gasturbochargers of a piston internal combustion engine and two exhaust gasbypass pipes;

FIG. 9 is a schematic representation of the blade row of thehigh-pressure turbine;

FIG. 10 is a schematic representation of the blade row of thelow-pressure turbine.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the invention, which are shown in the drawings, will bedescribed in detail in the following.

A charged, piston internal combustion engine 110, shown schematicallyaccording to FIG. 1, is equipped with an exhaust gas turbocharger 111which is connected continuously on the exhaust gas and charge air sideand is further connected with an exhaust gas turbocharger 112 which isconstructed so that it can be switchably disconnected and connected. Thecontinuously connected exhaust gas turbocharger 111, which provides thecharge air supply of the piston internal combustion engine during idlingand at low load, comprises an exhaust gas turbine 117 and a charge aircompressor 118. The disconnectable or switchable exhaust gasturbocharger 112 comprises an exhaust gas turbine 123 and a charge aircompressor 124.

The two exhaust gas turbochargers 111, 112 are supplied with exhaust gasfrom the piston internal combustion engine 110 via an exhaust gascollector pipe 125 by way of exhaust gas pipes 126, 127. The gasturbochargers 111, 112 supply their charge air by way of charge aircoolers 128 and charge air pipes 129, 130 into the charge air collectorpipe 131 of the piston internal combustion engine 110.

During idling and at low load of the piston internal combustion engine110, the exhaust gas turbocharger 112 is disconnected from the exhaustgas collector pipe 125 by an exhaust gas blocking device 133 controlledby the charge air pressure in the charge air collector pipe 131 via acontrol line 132. In this case, a charge air blocking device 134, in thesuction pipe 137, prevents charge air from flowing out of the charge aircollector pipe 131 by way of the exhaust gas turbocharger 112. All overthe compressor part of the disconnected exhaust gas turbocharger 112,the momentarily existing charge air pressure of the charge air collectorpipe 131 builds up from the charge air collector pipe 131 to in front ofthe charge air blocking device 134.

A bypass pipe 43, which is controlled by a controllable bypass blockingdevice 45, connects the suction pipe 137 of the charge air compressor124 of the switchable exhaust gas turbocharger 112 downstream of thecharge air blocking device 134 with the suction pipe 136 of the chargeair compressor 118 of the continuously connected exhaust gasturbocharger 111.

The bypass blocking device 45 has a locking part 52, as shown in detailin FIG. 2, which closes automatically as a result of the force of aspring 51 and is constructed as an oscillating flap which isnon-rotatably connected with a rotatable shaft 53. The rotatable shaft53, which extends to the outside through the housing 54 of the bypassblocking device 45, carries a lever 55 which is non-rotatably connectedwith it and to which the spring 51 is fastened. The closed position ofthe locking part 52, as shown in solid lines in FIG. 2, when theswitchable exhaust gas turbocharger 112 is disconnected, is locked in bya remote-controllable locking bar 56 which interacts with the lever 55.The locking bar 56 forms the piston rod of a piston 59 which is guidedin a housing 58 and, by a pressure spring 57, is brought into the lockedposition, and by a control pressure is brought into the unlockedposition. The control pressure is supplied by way of the control line 46which is connected with the control line 132 for the actuating of theexhaust gas blocking device 133.

When, during a power increase of the piston internal combustion engine110, an upper limit of the power range of the continuously switched-onexhaust gas turbocharger 111 is reached, the exhaust gas blocking device133 is opened under the control of the charge air pressure in the chargeair collector pipe 131 by way of the control line 132. As a result, thepreviously switched-off exhaust gas turbocharger 112 is acted upon byexhaust gas of the piston internal combustion engine.

Simultaneously with the opening-up of the exhaust gas blocking device133, the bypass blocking device 45 is unlocked by the pressure in thecontrol line 46. The pressure difference which still exists at thelocking part 52 at the start of the connecting operation and which isthe result of the difference of the excess pressure (charge airpressure), which is still present in the suction pipe 137 of the chargeair compressor 124 due to the disconnected state, and the low pressurein the suction pipe 136 of the charge air compressor 118, leads to theswinging-open of the locking part 52. As a result, an immediate pressurereduction of the excess pressure takes place in the suction pipe 137 byway of the bypass pipe 43 down to a pressure difference which is definedby a restoring force of the spring 51.

This means that, before a complete pressure compensation has takenplace, the locking part 52 returns to the locking position. The suctionpipes 136, 137 of the respective charge air compressors 118, 124 willtherefore be disconnected again. The connected starting charge aircompressor 124, while its begins to deliver, very rapidly reduces thestill remaining excess pressure in the suction pipe 137 assigned to it.As a result, the charge air blocking device 134 opens up concluding theconnecting operation.

Therefore, the connecting operation is concluded faster than in a casewhere, without the bypass pipe 43, the pressure reduction in the suctionpipe 137 would have to take place only by way of the beginning chargeair delivery of the connected switchable exhaust gas turbocharger 112.The power increase of the piston internal combustion engine 110 is nolonger limited by the connecting operation of an exhaust gasturbocharger.

By the rapid pressure reduction in the suction pipe 137 of the connectedcharge air compressor 124, the unacceptable overspeed of the runningparts is also avoided. The reason is that the power intake of the chargeair compressor 124 will now immediately, after the triggering of theconnecting operation, correspond to the power supplied by the exhaustgas turbine 123. The switchable exhaust gas turbocharger 112 will thenoperate at a permissible speed in the nominal range of itscharacteristic diagram.

FIG. 3 shows a charged, piston internal combustion engine 10 in whicheach exhaust gas turbocharger comprises a dual-stage exhaust gasturbocharger aggregate 11, 12 and the exhaust gas turbocharger aggregate12 is constructed so that it can be disconnected and connected. Thecontinuously switched-on exhaust gas turbocharger aggregate 11 comprisesa high-pressure exhaust gas turbocharger 13 having a high-pressureturbine 14 and a high-pressure compressor 15 as well as a low-pressureexhaust gas turbocharger 16 having a low-pressure turbine 17 and alow-pressure compressor 18. The exhaust gas turbocharger aggregate 12,which can be switched on and off, comprises a high-pressure exhaust gasturbocharger 19 having a high-pressure turbine 20 and a high-pressurecompressor 21 as well as a low-pressure exhaust gas turbocharger 22having a low-pressure turbine 23 and a low-pressure compressor 24. Theexhaust gas turbocharger aggregates 11 and 12 are supplied with exhaustgas via an exhaust gas collector pipe 25 by way of exhaust gas pipes 26and 27. The turbocharger aggregates 11 and 12 supply their charge airinto the piston internal combustion engine 10 by way of the charge aircooler 28, charge air pipes 29, 30 and by way of a charge air collectorpipe 31.

As described for the piston internal combustion engine according to FIG.1, a bypass pipe 43 is also arranged at the piston internal combustionengine 10 with dual-stage charging and is controlled by the bypassblocking device 45. However, in the case of the embodiment of thepresent invention as applied the piston, internal combustion engine 10according to FIG. 3, bypass pipe 43 connects the suction pipe 37 of thelow-pressure compressor 24 of the disconnectable exhaust gasturbocharger aggregate 12 downstream of a charge air blocking device 34with the suction pipe 36 of the low-pressure compressor 18 of theexhaust gas turbocharger aggregate 11 which is continuously connected.

Another bypass pipe 40 is provided which connects the suction pipe 38 ofthe high-pressure compressor 21 of the disconnectable exhaust gasturbocharger aggregate 12 with the suction pipe 39 of the high-pressurecompressor 15 of the exhaust gas turbocharger aggregate 11 which iscontinuously connected. In the additional bypass pipe 40, a by-passblocking device 41 is arranged which, by way of a control line 42, isconnected with the control line 32 for an exhaust gas blocking device33.

According to FIG. 4, the bypass blocking device 41, shown in FIG. 3, isequipped with a locking part 62 which is constructed as a flap and isnon-rotatably connected with a rotatable shaft 63. The shaft 63, whichextends to the outside through a housing 64, carries a lever 65 which isnon-rotatably connected thereto and which is coupled with an adjustingmechanism 66 which is remotely controlled by way of the control line 42.The closed position of the locking part 62, shown in solid lines in FIG.4, when the exhaust gas turbocharger aggregate 12 is switched off, islocked by a remotely controllable locking bar 56, as described for theembodiment of the present invention depicted by FIG. 3, which interactswith lever 65.

The switchable exhaust gas turbocharger aggregate 12 is also equippedwith a controllable exhaust gas bypass pipe 47 which extends from theexhaust gas blocking device 33 and, while bypassing the high-pressureturbine 20 of the high-pressure exhaust gas turbocharger 19, leads intoa low-pressure exhaust gas pipe 48 in front of the low-pressure turbine23 of the low-pressure exhaust gas turbocharger 22. The exhaust gas massflow to be branched from the high-pressure exhaust gas pipe 27 into theexhaust gas bypass pipe 47 can be determined by a correspondingdimensioning of the sectional area of flow of the exhaust gas bypasspipe 47 or by a flow control device which is not shown.

The exhaust gas blocking device 33 according to the arrangement shown inFIG. 5 is equipped with a first locking part 72 for blocking the exhaustgas pipe 27 which is constructed as a rotatable disk, is non-rotatablyconnected with a rotatable shaft 73 and is arranged upstream of thebranching-off point of the exhaust gas bypass pipe 47. A second lockingpart 74 of the blocking device 33 is coupled with the first locking part72 for blocking the exhaust gas bypass pipe 47. The coupling takes placein such a manner that the actuating of the exhaust gas blocking device33 for the opening-up of the exhaust gas pipe 27 causes a closing of theexhaust gas bypass pipe 47. An adjusting mechanism 76 for the actuatingof the exhaust gas blocking device 33 has a detent position 75 (shown inbroken lines) which can be released by a controllable stop 78, thisdetent position 75 being situated between about 10 and 60% of thecomplete opening of the first locking part 72. The second locking part74 is arranged with respect to the exhaust gas pipe 27 in such a mannerthat, in the case of detent position 75, a flow control effect isexercised on the exhaust gas pipe 27.

As a function of an operating value of the piston internal combustionengine 10 or of the exhaust gas turbocharger aggregate 12 which affectsthe controllable stop 78, after the removal of the stop 78, the exhaustgas blocking device 33 is further operated from the detent position 75to an end position 77 (shown in broken lines). When the end position 77of the locking part 72 is reached, the connecting operation of theturbocharger aggregate 12 is completed. In this case, the exhaust gasbypass pipe 47 will then be closed by the locking part 74 and thepassage in the exhaust gas pipe 27 is opened up completely.

During idling and low load of the piston internal combustion engine 10,the exhaust gas turbocharger aggregate 12 is disconnected from theexhaust gas collector pipe 25 by the exhaust gas blocking device 33which is controlled by the charge air pressure in the charge aircollector pipe 31 by way of the control line 32. In this case, thecharge air blocking device 34 in the suction pipe 37 of the low-pressurecompressor 24 prevents charge air from flowing out of the charge aircollector pipe 31 by way of the disconnected exhaust gas turbochargeraggregate 12. All over the compressor part of the disconnected exhaustgas turbocharger aggregate 12, the momentarily existing charge airpressure builds up from the direction of the charge air collector pipe31 to in front of the charge air blocking device 34.

When, in the case of a demand for an increasing power of the pistoninternal combustion engine, the upper power limit of the continuouslyswitched-on exhaust gas turbocharger aggregate 11 is reached, theexhaust gas blocking device 33, controlled by the charge air pressure inthe charge air collector pipe 31, is opened up and the previouslydisconnected exhaust gas turbocharger aggregate 12 is acted upon byexhaust gas of the piston internal combustion engine 10. Without anyspecial measure, the moving parts of the high-pressure exhaust gasturbocharger 19, after the connecting operation has been triggered,would be accelerated more than the running parts of the low-pressureexhaust gas turbocharger 22 and would very rapidly reach an unacceptablerotational speed. The cause is the smaller overall size as a result ofthermodynamic conditions and the resulting smaller mass moment ofinertia of the high-pressure exhaust gas turbocharger 19 in comparisonto the low-pressure exhaust gas turbocharger 22. Further, a delayedpressure reduction in the suction pipe 38 of the high-pressurecompressor 21 has a supporting effect on the unacceptable rotationalspeed increase. However, the low-pressure exhaust gas turbocharger 22,after the triggering of a connecting operation, suffers a delayedacceleration because the low-pressure turbine 23 does not immediatelyhave the required exhaust gas energy available because of thehigh-pressure turbine 20 connected in front of it. In order to avoid theswitching delay and the unacceptable rotational speed during theconnecting operation of the switchable exhaust gas turbochargeraggregate 12 comprising the high-pressure and low-pressure exhaust gasturbochargers 19, 22, three measures are simultaneously effective asdiscussed in detail below.

1. The opening-up of the exhaust gas blocking device 33 up to the detentposition 75 causes a restriction of the cross-section of the exhaust gaspipe 27 with a simultaneous opening of the exhaust gas bypass pipe 47.Immediately after the triggering of the connecting operation of theexhaust gas turbocharger aggregate 12, a part of the exhaust gas volumeflows directly into the low-pressure exhaust gas pipe 48 of thelow-pressure turbine 23. The exhaust gas volume for the high-pressureturbine 20 is reduced correspondingly.

2. The unlocking of the bypass blocking device 45 in the bypass pipe 43has the same effect on the pressure reduction in the suction pipe 37 asdescribed above for the embodiment according to FIG. 1. The pressurereduction in the suction pipe 37 provides the prerequisites for a rapiddelivery start of the low-pressure compressor 24 so that, after theconnecting operation, the driving power of the low-pressure turbine 23which is available early as a result of measure 1 discussed above, isalso taken off.

3. The actuating of the bypass blocking device 41 in the bypass pipe 40results in the pressure reduction in the suction pipe 38 of thehigh-pressure compressor 21 to the pressure level in the suction pipe 39of the continuously connected high-pressure compressor 15. This alsoprovides the prerequisite conditions for the high-pressure compressor 21for a regular delivery start. The driving power available at thehigh-pressure turbine 20 can therefore also be taken off by thehigh-pressure compressor 21.

The connected high-pressure compressor 21 can, in addition,independently of the momentary operating condition of the assignedlow-pressure compressor 24, by way of the bypass pipe 40, take in cooledair with an admission pressure matching the momentary operating pointfrom the pipe 39 of the continuously operating exhaust gas turbochargeraggregate 11. The loading of the high-pressure exhaust gas turbocharger19, by useful charge air delivery in connection with the initial exhaustgas volume reduced by measure 1, prevents that an undesirable overspeedof its moving parts is reached.

Via the exhaust gas bypass pipe 48, an earlier delivery start isachieved for the low-pressure exhaust gas turbocharger 22. In connectionwith the reduced acceleration of the high-pressure exhaust gasturbocharger 19, an approximate synchronization is achieved between thetwo which considerably shortens the course of a connecting operation andimproves the power increase for the piston, internal combustion engine.After the connecting operation of the exhaust gas turbocharger aggregate12 has taken place, the bypass pipe 40 may remain switched tothrough-flow because the same pressures exist in the connected suctionpipes 38 and 39 of the exhaust gas turbocharger aggregates 11, 12operating in parallel in the connecting operation. The locking part 62of the bypass blocking device 41 may also be constructed in the shape ofthe locking part 72 in the exhaust gas blocking device 33.

The effect of the exhaust gas mass flow supplied by way of the exhaustgas bypass pipe 47 of the low-pressure turbine 23 is also improved bythe fact that the introduction into the low-pressure exhaust pipe 48 ofthe low-pressure turbine 23 takes place in direct vicinity of thedischarge opening 251 of the high-pressure turbine 20 as shown in FIG. 3and FIGS. 6 and 7. The mouth of the exhaust gas bypass pipe 47 into thelow-pressure exhaust gas pipe 48 is constructed as a spiral housing 242,as shown in FIG. 6, so that the exhaust gas mass flow emerging from theexhaust gas bypass pipe 47 receives a swirl flow with a certain flowdirection 253. The spiral housing 242 is a component of an exchangeableconnecting piece 243 arranged between the high-pressure and thelow-pressure turbine 20, 23. Neither the housing of the high-pressureturbine 20 nor the housing of the low-pressure turbine 23 are affectedby the construction of the connection for the exhaust gas bypass pipe47. As a result, the same exhaust gas turbochargers may be used withoutany changes for the switchable exhaust gas turbocharger aggregate 12which are also used in the continuously connected exhaust gasturbocharger aggregate 11.

Referring to FIG. 9, the angular momentum becoming effective at theturbine blade row is proportional to the difference between thecircumferential component C_(UE) of the turbine entry flow C_(E) and thecircumferential component C_(UA) of the turbine exit flow C_(A). For acertain time period after the triggering of a connecting operation ofthe exhaust gas turbocharger aggregate 12, when the turbine blade row ofthe high-pressure turbine 19 is still standing still or is moving at alow rotational speed, the difference between the circumferentialcomponents C_(UE) and C_(UA) is large. This is the result of the factthat, in the starting phase of the turbine wheel, a strong deflection ofthe flow takes place in the turbine blade row and the circumferentialcomponent C_(UA) of the turbine exit flow C_(A) is directed against theactual rotating direction 252 of the turbine blade row (FIG. 9). Theflow direction 253 of the swirl flow, which is generated by the exhaustgas mass flow entering from the exhaust gas bypass pipe 47 into theoutflow range of the high-pressure turbine 20, is directed against thecircumferential component C_(UA) of the turbine exit flow C_(A) in thisoperating range. This results in a reduction of the circumferential flowon the turbine exit side which influences the angular momentum so thatthe angular momentum which is effective at the turbine blade row of thehigh-pressure turbine 20 is also reduced in this operating condition.The torque for the acceleration of the running parts of thehigh-pressure exhaust gas turbocharger 19 which is reduced in thismanner prevents the occurrence of an undesirable overspeed after aconnecting operation.

At the same time, an advanced charge air delivery start occurs for thelow-pressure exhaust gas turbocharger 22 with the exhaust gas mass flowfrom the exhaust gas bypass pipe 47. In connection with the reducedacceleration of the high-pressure exhaust gas turbocharger 19, anapproximate synchronization is obtained between the operation of the twosuperchargers which considerably decreases the course of a connectingoperation and improves the power increase for the piston internalcombustion engine 10.

Another improvement of the synchronization between the high-pressure andthe low-pressure exhaust gas turbocharger 19, 22, after the connectingoperation and of the power increase behavior of the piston internalcombustion engine 10, is achieved by an arrangement of anotherembodiment shown in FIG. 8. An exhaust gas bypass pipe 236 whichbranches off from the exhaust gas bypass pipe 47 also leads to anexhaust gas pipe 239. As seen in FIGS. 6 and 7, the mouth of the exhaustgas bypass pipe 236 leading into the exhaust gas pipe 239 is arranged indirect proximity of the outflow opening 251' of the low-pressure turbine23 and is also constructed as a spiral housing 242' at an exchangeableconnecting piece 243'. The exhaust gas mass flow can be controlled by aflow control device 255 arranged in the exhaust gas bypass pipe 236 asseen in FIG. 8.

The exhaust gas mass flow emerging from the exhaust gas bypass pipe 236generates a swirl flow in the exhaust gas pipe 239 which is directed insuch a manner that after the triggering of a connecting operation, apositive influence occurs on the power of the low-pressure turbine 23.

As shown in FIG. 10, it also applies to the situation at thelow-pressure turbine, that the angular momentum becoming effective atthe turbine blade row is proportional to the difference between thecircumferential component C_(UE) ' of the turbine entry flow C_(E) ' andthe circumferential component C_(UA) ' of the turbine exit flow C_(A) '.

FIG. 10 shows the flow conditions at the turbine blade row of thelow-pressure turbine 23 after a connecting operation while the runningparts of the low-pressure exhaust gas turbocharger 22 are still standingstill or are moving at a low rotational speed. The flow direction 253'of the swirl flow, which is generated by the exhaust gas mass flowentering from the exhaust gas bypass pipe 236 into the outflow area ofthe low-pressure turbine 23, in this operating range, has the samedirection as the circumferential component C_(UA) ' of the turbine exitflow C_(A) '. The result is an increase of the circumferential flow onthe turbine exit side affecting the angular momentum, so that theangular momentum which is in effect at the turbine blade row of thelow-pressure turbine 23 also increases in the direction of the actualrotating direction 254.

The torque increase at the low-pressure turbine 23, which can beachieved by the additional exhaust gas bypass pipe 236, in connectionwith the partial exhaust gas volume supplied by way of the exhaust gasbypass pipe 47 of the low-pressure turbine 23, causes a fastacceleration of the running parts of the low-pressure exhaust gasturbocharger 22 after a connecting operation. As a result, the powerexcess is increased which is required for a fast delivery start of thelow-pressure compressor 24 after a connecting operation.

The combination of the power intake of the high-pressure exhaust gasturbocharger 19 which is reduced for a short time after a connectingoperation with the simultaneously increased power intake of thelow-pressure exhaust gas turbocharger 22 and the other measures avoids anoticeable switching delay for the exhaust gas turbocharger aggregate12. At the same time, the occurrence of an overspeed is prevented at thehigh-pressure exhaust gas turbocharger.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

We claim:
 1. A control arrangement for a charged, piston internalcombustion engine having a plurality of exhaust gas turbochargersincluding at least one switchable exhaust gas turbocharger which isselectively operated and a continuously connected exhaust gasturbocharger operating in parallel therewith, each of the plurality ofexhaust gas turbochargers having an exhaust gas turbine connected to anexhaust gas pipe and a charge air compressor connected to a suctionpipe, the arrangement comprising:a controllable exhaust gas blockingdevice for blocking passage of exhaust gas to the exhaust gas turbine ofthe at least one switchable exhaust gas turbocharger; an automaticallyoperating charge air blocking device for blocking the suction pipe ofthe charge air compressor of the at least one switchable gasturbocharger; a bypass pipe connecting the suction pipe of the chargeair compressor of the at least one switchable gas turbocharger, at apoint upstream from the automatically operating charge air blockingdevice, with the suction pipe of the charge air compressor of thecontinuously connected exhaust gas turbocharger at a point upstream ofthe automatically operating charge air blocking device; and a bypassblocking device for controllably blocking the bypass pipe.
 2. A controlarrangement for a charged, piston internal combustion engine acording toclaim 1, wherein the bypass blocking device has a locking part whichlocks automatically in a direction towards the suction pipe of thecharge air compressor of the at least one switchable exhaust gasturbocharger.
 3. A control arrangement for a charged, piston internalcombustion engine according to claim 2, wherein the locking partinteracts with a locking device arranged in the bypass blocking devicefor locking the locking part at a closed position.
 4. A controlarrangement for a charged, piston internal combustion engine accordingto claim 3, wherein the locking device is remotely controlled by acontrol line connected with a control line for operating thecontrollable exhaust gas blocking device.
 5. A control arrangement for acharged, piston internal combustion engine having a plurality of exhaustgas turbochargers including at least one switchable exhaust gasturbocharger which is selectively operated and a continuously connectedexhaust gas turbocharger operating in parallel therewith, each of theexhaust gas turbochargers comprise a high-pressure exhaust gasturbocharger having a high-pressure turbine connected to an exhaust gaspipe and a high-pressure compressor connected to a suction pipe, and alow-pressure exhaust gas turbocharger having a low-pressure turbineconnected to an exhaust gas pipe and a low-pressure compressor connectedto a suction pipe, the arrangement comprising:a controllable exhaust gasblocking device for blocking passage of exhaust gas to the at least oneswitchable exhaust gas turbocharger; an automatically operating chargeair blocking device for blocking passage of suction gas to the at leastone switchable gas turbocharger; a bypass pipe connecting the suctionpipe of the low-pressure compressor of the continuously connectedexhaust gas turbocharger to the suction pipe of the low-pressurecompressor of the switchable exhaust gas turbocharger down stream of theautomatically operating, charge air blocking device; and a bypassblocking device for controllably blocking the bypass pipe.
 6. A controlarrangement for a charged, piston internal combustion engine acording toclaim 5, wherein the bypass blocking device has a locking part whichlocks automatically in a direction towards the suction pipe of thecompressor of the at least one switchable exhaust gas turbocharger.
 7. Acontrol arrangement for a charged, piston internal combustion engineaccording to claim 6, wherein the locking part interacts with a lockingdevice arranged at the bypass blocking device for locking the lockingpart in a closed position.
 8. A control arrangement for a charged,piston internal combustion engine according to claim 6, wherein thelocking device is remotely controlled by a control line connected with acontrol line for operating the controllable exhaust gas blocking device.9. A control arrangement for a charged, piston internal combustionengine according to claim 5, further comprising an additional bypasspipe connecting a suction pipe of the high-pressure compressor of thecontinuously connected exhaust gas turbocharger, and a suction pipe ofthe high-pressure compressor of the switchable exhaust gas turbocharger.10. A control arrangement for a charged, piston internal combustionengine according to claim 9, wherein a locking part of a bypass blockingdevice in the additional bypass pipe can be remotely controlled by acontrol line connected with the control line for operating thecontrollable exhaust gas blocking device.
 11. A control arrangement fora charged, piston internal combustion engine according to claim 5,wherein an exhaust gas bypass pipe leads from the controllable exhaustgas blocking device into a low-pressure exhaust gas pipe which feeds thelow-pressure turbine of the low-pressure exhaust gas turbocharger of theswitchable exhaust gas turbocharger.
 12. A control arrangement for acharged, piston internal combustion engine according to claim 11,wherein the controllable exhaust gas blocking device includes a firstlocking part for an exhaust gas pipe leading from the engine and asecond locking part coupled to the first locking part, for the exhaustgas bypass pipe whereby an opening of the first locking part causes aclosing of the second locking part.
 13. A control arrangement for acharged, piston internal combustion engine according to claim 12,wherein the exhaust gas blocking device has a detent position which isin effect between about 10 to 60% of a full opening of the first lockingpart and wherein the position of the second locking part influences across-section of the exhaust gas pipe.
 14. A control arrangement for acharged, piston internal combustion engine according to claim 11,wherein a mouth of the exhaust gas bypass pipe is arranged in directproximity of an outflow opening of the high-pressure turbine of theswitchable turbocharger and wherein exhaust gas mass flow emerging fromthe exhaust gas bypass pipe generates a swirl flow in the low-pressureexhaust gas pipe of the switchable turbocharger, a flow direction ofthis swirl flow being directed against an exit swirl of thehigh-pressure turbine of the switchable turbocharger occurring after aconnecting operation during a starting of the high-pressure exhaust gasturbocharger of the switchable turbocharger.
 15. A control arrangementfor a charged, piston internal combustion engine according to claim 14,wherein an additional exhaust gas bypass pipe branches off the exhaustgas bypass pipe, a mouth of the additional exhaust gas bypass pipe beingarranged in direct proximity of an outflow opening of the low-pressureturbine of the switchable turbocharger in an exhaust gas pipe thereof.16. A control arrangement for a charged, piston internal combustionengine according to claim 15, wherein the exhaust gas mass flow emergingfrom the exhaust gas bypass pipe generates a swirl flow in the exhaustgas pipe of the low-pressure turbine of the switchable turbocharger, theflow direction of this swirl flow being the same as that of an exitswirl of the low-pressure turbine of the switchable turbochargeroccurring during the starting of the low-pressure exhaust gasturbocharger of the switchable turbocharger after a connectingoperation.
 17. A control arrangement for a charged, piston internalcombustion engine according to claim 15, wherein the mouth of exhaustgas bypass pipe and of exhaust gas bypass pipe are constructed as aspiral housing.
 18. A control arrangement for a charged, piston internalcombustion engine according to claim 17, wherein the connection of theexhaust gas bypass pipe and of the exhaust gas bypass pipe is anexchangeable connecting piece.
 19. A control arrangement for a charged,piston internal combustion engine according to claim 15, wherein a flowcontrol device which influences a mass throughput is arranged in theexhaust gas bypass pipe.